The present invention relates to an improvement of a muffler assembly of an internal combustion engine.
An internal combustion engine is provided with an exhaust port to which a front end portion of an exhaust pipe is connected and through which an engine exhaust gas is exhausted, and a muffler is connected to a rear end portion of the exhaust pipe to silence noise of the exhaust gas, which is thereafter exhausted outward.
A conventional muffler of an internal combustion engine is generally composed of an outer casing defining therein a plurality of silencer chambers divided by means of partitions in a row. The exhaust pipe is connected to the frontside the silencer chamber and a tail pipe is connected to the rearside silencer chamber. The respective silencer chambers are communicated with baffle pipes to thereby silence the noise of the exhaust gas and then exhaust the gas outward through the tail pipe. Such a muffler is disclosed in, for example, Japanese Utility Model Laid-open Publication No. 63-196414 or No. 63-93411.
The exhaust gas passing the exhaust pipe and flowing in the silencer chamber is compressed to a relatively high pressure, and particularly, in the frontmost silencer chamber, the inner wall of the casing is impacted or shocked by the intermittent pressure pulsation of the exhaust gas, thus causing metallic noise. In order to obviate this defect, i.e. to reduce or silence the noise, a sound absorption material such as glass wool is applied to the inner surface of the casing, this working, however, being troublesome and involving increased manufacturing cost.